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Modern Computer Systems
- an Overview
In this lecture we discuss the following material:
• what makes up a computer system
• the internals of a computer
• software (makes the computer useable)
• various types of computers
Covering Unit 1 of the text by Norton
The Parts of a Computer System
What is a Computer?
The Parts of a Computer System
- What is a Computer?
A computer is an electronic device used to process data.
A computer can convert data into information that is
useful to people.
A complete computer system includes four distinct
The Parts of a Computer System - Hardware
A computer's hardware consists of electronic
devices; the parts you can see and touch.
The term "device" refers to any piece of hardware
used by the computer, such as a keyboard, monitor,
modem, mouse, etc.
The Parts of a Computer System - Software
Software – also called programs – consists of
organized sets of instructions for controlling the
Some programs exist for the computer's use, to help
it manage its own tasks and devices.
Other programs exist for the user, and enable the
computer to perform tasks for you, such as creating
The Parts of a Computer System - Data
Data consists of raw facts, which the computer can
manipulate and process into information that is
useful to people.
Computerized data is digital, meaning that it has
been reduced to digits, or numbers. The computer
stores and reads all data as numbers.
Although computers use data in digital form, they
convert data into forms that people can
understand, such as text, numerals, sounds, and
The Parts of a Computer System – Users
People are the computer's operators, or users.
Some types of computers can operate without
much intervention from people, but personal
computers are designed specifically for use by
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Looking Inside the Machine - The CPU
The procedure that
transforms raw data
into useful
information is called
processing. This
function is divided
between the
computer's processor
and memory.
The processor
is also called
the central
unit (CPU). It
manages all
devices and
performs the
processing of
The CPU consists of one or more chips attached to the
computer's main circuit board (the motherboard).
Looking Inside the Machine - Memory
Memory also consists of chips attached to the
Memory holds data and program instructions as
the CPU works with them. This memory is called
Random Access Memory (RAM).
The CPU can find any piece of data
in RAM, when it needs it for processing.
RAM is volatile, meaning it holds data
only when the power is on. When the power
is off, RAM's contents are lost.
Looking Inside the Machine
– How Memory is Measured
The smallest usable unit of measure for memory is
the byte – the amount of memory required to hold
one character, like the letter A or the numeral 2.
Computers work with larger chunks of data,
measured in multiple bytes, as shown below:
Approx. Value
Actual Value
Kilobyte (KB)
Megabyte (MB)
Gigabyte (GB)
Terabyte (TB)
Looking Inside the Machine –
Input and Output Devices
Input devices accept data and instructions from the
user or from another computer system. The keyboard
and mouse are examples of input devices.
Output devices return processed data back to the user
or to another computer system. The printer and
monitor are examples.
Communications devices (such as modems and
network interface cards) perform both input and
output, allowing computers to share information.
Looking Inside the Machine - Storage Devices
Storage devices hold data not currently being used
by the CPU. Data is commonly stored on a magnetic
or optical disk. Each type uses a special medium for
storing data on its surface.
A disk drive is a device that reads data from and
writes data to a disk. Most new computers feature a
floppy disk drive, a hard disk drive, and an optical
disk drive.
The most common optical storage devices are CDROM and DVD-ROM drives.
Software: Bringing the Machine to Life
What is Software?
System Software
Application Software
Bringing the Machine to Life –
What is Software?
Software is a set of electronic instructions that tells the
computer how to do certain tasks. A set of instructions
is often called a program.
When a computer is using a particular program, it is
said to be running or executing the program.
The two most common types of programs are system
software and application software.
Bringing the Machine to Life –
System Software
System software exists primarily for the computer
itself, to help the computer perform specific
One major type of system software is the operating
system (OS). All computers require an operating
The OS tells the computer how to interact with the
user and its own devices.
Common operating systems include Windows, the
Macintosh OS, OS/2, and UNIX .
Bringing the Machine to Life - Applications
Application software tells the computer how to
accomplish tasks the user requires, such as creating a
document or editing a graphic image.
Some important kinds of application software are:
Word processing programs
Database management
Graphics programs
Web design tools and browsers
Communications programs
Entertainment and education
Spreadsheet software
Presentation programs
Networking software
Internet applications
Multimedia authoring
The Shapes of Computers Today
- Supercomputers
Supercomputers are the most powerful computers.
They are used for problems requiring complex
Because of their size and expense, supercomputers
are relatively rare.
Supercomputers are used by universities,
government agencies, and large businesses.
The Shapes of Computers Today
- Mainframe Computers
Mainframe computers can support hundreds or
thousands of users, handling massive amounts of
input, output, and storage.
Mainframe computers are used in large
organizations where many users need access to
shared data and programs.
Mainframes are also used as e-commerce servers,
handling transactions over the Internet.
The Shapes of Computers Today
- Minicomputers
Minicomputers are smaller than mainframes but
larger than microcomputers.
Minicomputers usually have multiple terminals.
Minicomputers may be used as network servers and
Internet servers.
The Shapes of Computers Today –
Workstations are powerful single-user computers.
Workstations are used for tasks that require a great
deal of number-crunching power, such as product
design and computer animation.
Workstations are often used as network and Internet
The Shapes of Computers Today –
Microcomputers, or Personal Computers
Microcomputers are more commonly known as
personal computers. The term "PC" is applied to
IBM-PCs or compatible computers.
Full-size desktop computers are the most common type
of PC.
Notebook (laptop) computers are used by people who
need the power of a desktop system, but also
Handheld PCs (such as PDAs) lack the power of a
desktop or notebook PC, but offer features for users
who need limited functions and small size.
List the four parts of a computer system.
Identify four types of computer hardware.
Provide examples of input and output devices.
Name and describe three types of storage devices.
Differentiate the two main categories of software.
List the five most common types of computer systems.
Differentiate workstations from personal computers.
Identify four types of personal computers.

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